In certain semiconductor devices such as dynamic threshold MOS (Dt-MOS) transistors, SRAMs, and the like, there arise cases in which a gate electrode is connected electrically to a surface of a semiconductor substrate by way of so-called shared contact plug.
A shared contact plug is a kind of via-plug usually formed in an elongated opening of an interlayer insulation film covering a gate electrode to electrically connect the gate electrode with the surface of a semiconductor substrate. The elongated opening exposes a top surface of the gate electrode and further a surface of a semiconductor substrate, and because of this, a shared contact plug generally has an elongating shape corresponding to the shape of the elongating opening. Usually, a gate electrode carries sidewall insulation films, and because of this, a shared contact has a tendency to extend from the top surface of the gate electrode to a distance beyond the sidewall insulation film in order to attain the contact with the surface of a semiconductor substrate. Thus, there has been a problem that a shared contact occupies a large area.